The disclosure concerns a damping device, in particular for damping pressure pulses in a brake circuit of a slip-controllable hydraulic vehicle brake system. Such damping devices are disclosed for example in DE 10 2011 089 183 A1.
Slip-controllable brake systems, also known as ESP brake systems, support the driver in critical driving situations. The trade distinguishes various operating modes of these brake systems, namely a passive, a partly active or a fully active brake mode.
In passive brake mode, the wheel brake pressure is generated by the driver, e.g. by actuation of a brake pedal.
In partly active mode, the pressure in the brake system is higher than established by the driver, which means that the brake pressure generated by the driver is amplified by the brake system.
In fully active mode however, the driver does not actuate the brake pedal at all and the brake pressure is provided solely by a pressure generator provided in the brake system.
Mostly, reciprocating piston pumps are used as pressure generators. One or more piston pumps may be assigned to each brake circuit of the vehicle brake system. In principle, reciprocating piston pumps work cyclically, whereby the pressure is built up not evenly and linearly, but in stages depending on the delivery behavior of the pump element. The pressure pulses of reciprocating piston pumps are audible in the vehicle interior and/or perceptible as vibrations at the brake pedal. Both are undesirable from a comfort aspect.
In order to smooth out pressure pulses, therefore, damping devices are provided downstream of the pressure generator. As disclosed in DE 102011089183 A1, these damping devices provide a combination of a pressure-medium capacity with a pressure-medium receiving volume which varies depending on brake pressure, and a downstream flow resistance. The latter may be configured as a constant choke with a fixed flow cross-section, or as a dynamic choke with a flow cross-section which varies pressure-dependently.
One undesirable side effect of these damping measures is that the pressure-medium volume taken up by the pressure-medium capacity is not available for building up brake pressure, and therefore in passive operating mode of the vehicle brake system, i.e. when the brake pressure is generated by the driver, the pedal travel required to build up a specific brake pressure at the brake master cylinder is extended.
It would be possible to limit the pedal travel extension by limiting the receiving volume of the damping device, but this would result in less effective damping properties in the partly active or fully active brake mode.
In this context, the object of the refinement of damping devices is to maintain or improve their damping properties without extending the pedal travel required for generating the brake pressure in passive operating mode of the vehicle brake system.